DoubleH wrote:
Microsoft Security Essentials is pro(its free and hell they put there name on it its pretty good / not super invasive)
On another note nothing really "stops" virus's, they only detect them after you have them already. So don't DL anything from "untrusted sources" and just get a porno/torrent comp and reinstall the OS every time shit hits the fan.
The point behind real-time scanning of executables before they're run is to do exactly what you said it didn't.
It's not terribly difficult to take control of the executable handler. Of course, the same can be done maliciously, but that would require a vulnerability in the part of the scanner.
Yes, if you get 0day'd then you're boned. But that's incredibly rare since the majority of infections come from malware that's been around for a while.
PS: Virtual machine > building a whole second computer for downloading from piss poor sites.